20 March 1966: At Edwards Air Force Base in the high desert of southern California, Hughes Aircraft Company test pilot Jack L. Zimmerman flew the third prototype YOH-6A Light Observation Helicopter, 62-4213, to set a Fédération Aéronautique Internationale (FAI) World Record for Distance Over a Closed Circuit Without Landing of 1,700.12 kilometers (1,056.41 miles).¹ Fifty-one years later, this record still stands.
One week later, Zimmerman would set six more World Records ² with the “Loach.”
The Hughes Model 369 was built in response to a U.S. Army requirement for a Light Observation Helicopter (“L.O.H.”). It was designated YOH-6A, and the first aircraft received U.S. Army serial number 62-4211. It competed with prototypes from Bell Helicopter Company (YOH-4) and Fairchild-Hiller (YOH-5). All three aircraft were powered by a lightweight Allison Engine Company turboshaft engine. The YOH-6A won the three-way competition and was ordered into production as the OH-6A Cayuse. It was nicknamed “loach,” an acronym for L.O.H.
The YOH-6A was a two-place light helicopter, flown by a single pilot. It had a four-bladed, articulated main rotor which turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right.) Stacks of thin stainless steel “straps” fastened the rotor blades to the hub and were flexible enough to allow for flapping and feathering. Hydraulic dampers controlled lead-lag. Originally, there were blade cuffs around the main rotor blade roots in an attempt to reduce aerodynamic drag, but these were soon discarded. A two-bladed semi-rigid tail rotor was mounted on the left side of the tail boom. Seen from the left, the tail-rotor rotates counter-clockwise. (The advancing blade is on top.)
The YOH-6A was powered by a T63-A-5 turboshaft engine (Allison Model 250-C10) mounted behind the cabin at a 45° angle. The engine was rated at 212 shaft horsepower at 52,142 r.p.m. (102% N1) and 693 °C. turbine outlet temperature for maximum continuous power, and 250 shaft horsepower at 738 °C., 5-minute limit, for takeoff. Production OH-6A helicopters used the slightly more powerful T63-A-5A (250-C10A) engine.
The Hughes Tool Company Aircraft Division built 1,420 OH-6A Cayuse helicopters for the U.S. Army. The helicopter remains in production as AH-6C and MH-6 military helicopters, and the MD500E and MD530F civil aircraft.
Hughes YOH-6A 62-4213 is in the collection of the United States Army Aviation Museum, Fort Rucker, Alabama.
Jack Louis Zimmerman was born 1 September 1921 at Chicago, Illinois, the second of three children of Bernard Zimmerman, an electrician, and Esther Rujawski Zimmerman. He studied engineering at the University of Chicago, but left to enlist in the U.S. Army Air Corps. He graduated from flight school in 1943 and was commissioned a second lieutenant.
Lieutenant Zimmerman was sent to Freeman Field, Indiana, as part of the Army’s first class of student helicopter pilots, training on the Sikorsky R-4. On completion of training he was assigned to a Liberty ship in the western Pacific as part of a Project Ivory Soap Aviation Repair Unit.
Taking off from the Army Transport Serviceship SS Maj. Gen. Robert Olds (formerly, the Liberty ship, SS Daniel E. Garrett), Lieutenant Zimmerman’s helicopter crashed into the sea. For his heroic actions in saving a passenger’s life, he was awarded the Soldier’s Medal:
“For heroism displayed in rescuing an enlisted man from drowning on 1 November 1944. While taking off from the flight deck of the SS Daniel E. Garrett, Lieutenant Zimmerman with Private William K. Troche as passenger was forced to land at sea. Lieutenant Zimmerman at the risk of his life made several dives into the plane when his passenger had difficulty in extricating himself from the craft. When Private Troche’s life preserver failed to operate properly, Lieutenant Zimmerman supported him in the water for approximately 30 minutes and afterwards pulled him to a life preserver, which had been thrown from the ship. The heroism displayed by Lieutenant Zimmerman on this occasion reflects great credit upon himself and the military service.” —http://collectair.org/zimmerman.html
Following World War II, Jack Zimmerman was employed as a commercial pilot, and then a test pilot for the Seibel Helicopter S-4 and YH-24 light helicopters, and when the company was bought by Cessna, he continued testing the improved Cessna CH-1 and UH-41 Seneca. In 1963, Zimmerman began working as a test pilot for the Hughes Tool Company’s Aircraft Division. He retired in 1982.
Jack Louis Zimmerman died at San Diego, California, on his 81st birthday, 1 September 2002.
¹ FAI Record File Number 762
² FAI Record File Numbers 771, 772, 9920, 9921, 9922, and 9923
© 2017, Bryan R. Swopesby
20 March 1945: Tony LeVier was conducting a test flight of the first prototype Lockheed XP-80A, 44-83021, near Muroc Army Air Field (now known as Edwards Air Force Base).
The XP-80A was developed from the original XP-80 prototype, but was larger to incorporate a more powerful General Electric I-40 turbojet engine in place of the original Allis-Chalmers J36 (a license-built version of the British Halford H.1B). The I-40 was a single-shaft turbojet which used a double-inlet, single-stage, centrifugal-flow compressor, fourteen straight-through combustors and a single-stage axial-flow turbine. The engine had a maximum speed of 11,500 r.p.m. and produced 4,000 pounds of thrust (17.79 kilonewtons). The I-40 was 48 inches (1.2 meters) in diameter and weighed 1,820 pounds (826 kilograms). The I-40 would be produced by Allison as the J33-series.
At 15,000 feet (4,572 meters), LeVier put the XP-80A into a dive, intending to level off at 10,000 feet (3,048 meters) for a high-speed run. However, at 11,000 feet (3,353 meters), the single-stage axial-flow turbine inside the jet engine failed and fragments tore through the prototype’s fuselage. The tail section of the airplane was cut off and the XP-80A went out of control.
The XP-80A was not equipped with an ejection seat and LeVier had difficulty getting out, but finally escaped at about 4,000 feet (1,219 meters).
44-83021 crashed near the town of Rosamond and was completely destroyed. Tony LeVier’s parachute was swinging and he was severely injured when he hit the ground. His injuries kept him from flying for the next six months.
The Lockheed XP-80A was a single-place, single engine prototype fighter. It was 34 feet, 6 inches (10.516 meters) long with a wingspan of 39 feet, 0 inches (11.887 meters) and overall height of 11 feet, 4 inches (3.454 meters). It had an empty weight of 7,225 pounds (3,277 kilograms) and gross weight of 9,600 pounds (4,354 kilograms).
Armament consisted of six Browning .50-caliber AN-M2 (12.7 × 99 NATO) machine guns with 300 rounds of ammunition per gun.
Two XP-80As were built. These were followed by twelve YP-80A Shooting Star service test aircraft. The Lockheed P-80A Shooting Star was ordered into production with an initial contract for 500 aircraft. This was soon followed by a second order for 2,500 fighters.
© 2017, Bryan R. Swopesby
20 March 1937: After completing repairs and preparation for the second leg of her around-the-world flight—Hawaii to Howland Island—Amelia Earhart’s Lockheed Electra 10E, NR16020, was moved from Wheeler Field to Luke Field on Ford Island on 19 March to take advantage of the longer, fully paved runway.
Paul Mantz had warmed the engines at 5:00 a.m., 20 March, then shut them down. He would not be aboard for this flight. Amelia Earhart, Captain Manning and Captain Noonan boarded the Electra at 5:30 a.m. and Earhart restarted the engines. At 5:40 a.m., she began to taxi to the northeast corner of the runway. Weather was good, with a ceiling of 3,000 feet, visibility 3,500 feet in pre-dawn darkness, and wind from the south at 2 miles per hour.
At 5:53 a.m., Amelia Earhart accelerated for takeoff. A United States Army Board of Investigation report describes what happened next:
On reaching the end Miss Earhart turned and after a brief delay opened both throttles. As the airplane gathered speed it swung slightly to the right. Miss Earhart corrected this tendency by throttling the left hand motor. The airplane then began to swing to the left with increasing speed, characteristic of a ground loop. It tilted outward, right wing low and for 50 or 60 feet was supported by the right wheel only. The right-hand landing-gear suddenly collapsed under this excessive load followed by the left. The airplane spun sharply to the left on its belly amid a shower of sparks from the mat and came to rest headed about 200 degrees from its initial course. There was no fire. Miss Earhart and her crew emerged unhurt. The visible damage to the airplane was as follows:- Right wing and engine nacelle severely damaged, left engine nacelle damaged on under side, right hand rudder and end of stabilizer bent. The engines were undamaged. The oil tanks were ruptured. . . .
FINDINGS: . . . after a run of 1200 feet the airplane crashed on the landing mat due to collapse of the landing gear as a result of an uncontrolled ground loop; the lack of factual evidence makes it impossible to establish the reason for the ground loop; that as a result of the crash the airplane was damaged to an extent requiring major overhaul. . . .
—excerpts from PROCEEDINGS OF A BOARD OF OFFICERS CONVENED TO INVESTIGATE THE CRASH OF MISS AMELIA EARHART AT LUKE FIELD, 20 MARCH 1937
The Electra was extensively damaged. There were no injuries, but the Electra was sent back to Lockheed at Burbank, California, aboard the passenger liner, SS Lurline, for repair.
At the time of the accident, NR16020 had flown 181 hours, 17 minutes, total time since new (TTSN).
© 2017, Bryan R. Swopesby
20 March 1922: USS Langley (CV-1) was commissioned as the first aircraft carrier of the United States Navy. It was a former collier, USS Jupiter (AC-3), which had been converted at the Norfolk Navy Yard, 1921–1922.
The aircraft carrier was powered by General Electric turbo-electric drive, with a total of 7,200 shaft horsepower. 542 feet (165 meters) in length, she could make 15.5 knots (28.7 kilometers per hour). Her full load displacement was 14,100 tons.
As more modern aircraft carriers Lexington and Saratoga came in to service, Langley was once again converted, this time to a sea plane tender, AV-3. She was badly damaged by Japanese dive bombers, 27 February 1942, and was scuttled.
More aircraft carriers would follow and were the key to the United States Navy victory in the Pacific Ocean, bringing World War II to a close.
Ninety-five years after USS Langley was commissioned, the aircraft carrier is the center of the American fleet. The Nimitz-class carriers are the most powerful warships ever built.
© 2016, Bryan R. Swopesby